Recently, mobile wireless equipment such as mobile telephones has become common; such a mobile telephone is provided with an antenna for transmitting and receiving calls and/or information. Typically, this antenna is in the form of a whip antenna that can be freely extended/retracted and that can be accommodated in the casing of the mobile telephone for convenience in carrying when the mobile telephone is on standby.
However, since, when the whip antenna is accommodated in the casing, the mobile telephone is substantially incapable of transmission and reception, a helical antenna comprising a small coil element that is positioned outside the casing even when the whip antenna is accommodated in a casing may be provided at the tip of the whip antenna. In this way, when the whip antenna is accommodated in the casing, transmission and reception can be performed by using this helical antenna.
FIG. 11 shows an example of the construction of a prior art antenna for mobile wireless equipment in such an antenna for mobile wireless equipment.
In the case of the antenna 300 for mobile wireless equipment shown in this Figure, a linear whip antenna section 313 is freely slidably inserted into an antenna holder 314 made of metal such that the whip antenna section 313 can be freely extended and retracted with respect to the casing when the antenna holder 314 is fixed to the casing of the mobile wireless equipment. An insulating joint 312 that extends to a top section 310 is integrally formed passing through the interior of a top plug 311, at the tip of the whip antenna section 313, and a stop 315 made of metal is fixed to the other end thereof. The stop 315 is inserted into the antenna holder 314 when the whip antenna section 313 is extended, so that the whip antenna section 313 is electrically connected with the antenna holder 314 through the stop 315.
Also, the joint 312 is integrally formed at the tip of the whip antenna section 313 and is insertion-formed with the top plug 311 when this integral forming is performed. The top of this joint 312 is not shown in the drawings, but the top section 310 and the whip antenna section 313 are fixed such that the top of this joint 312 extends within the top section 310 and the top section 310 and the whip antenna section 313 are positioned substantially coaxially. In addition, although not shown, the top of the top plug 311, which is made of metal, is positioned within the top section 310, an end section of the helical antenna accommodated in the top section 310 being electrically connected therewith. In this way, when the whip antenna section 313 is accommodated, the helical antenna is electrically connected with the antenna holder 314 through the top plug 311 by insertion of the top plug 311 from above into the antenna holder 314.
However, in recent years, with the development and use of various types of mobile communications system, demands have increased for transmitting or receiving between a plurality of communications systems using a single item of mobile wireless equipment. For example, mobile wireless equipment is being demanded that is capable of receiving position measurement information from the GPS (Global Positioning System) system, in order to enable the user who is carrying the mobile telephone equipment to ascertain his current position, in addition to transmission/reception with a mobile wireless system as performed hitherto.
However, in order to achieve a construction that is capable of operation with a plurality of communication systems including the GPS system in a single item of mobile wireless equipment, it was necessary for example to incorporate a planar antenna for GPS or to install a small-volume chip antenna in the casing, in addition to the antenna 300 for the mobile wireless equipment, as shown in FIG. 11 described above; this therefore led to the problem of tending to increase the size of the mobile wireless equipment.
Also, there is the problem that, since the mobile wireless equipment is employed held in the user's hand, if a GPS antenna is provided in the casing, the proportion of the GPS antenna that is covered by the hand of the user holding the equipment becomes large, adversely affecting the electrical performance.
An object of the present invention is therefore to provide a multi-frequency antenna capable of performing communication with another communication system in addition to communication with the mobile wireless system, as hitherto, without causing deterioration of the electrical properties when employed by the user or increase in the overall size of the mobile wireless equipment.